Spray atomization of alternative fuels in medium speed diesel engines

摘要

Until today, the diesel engine is still the most important power source for heavy duty road & rail transport, marine, genset and agriculture applications. The decreasing reserves of fossil fuels, the strict emission regulations, the greenhouse effect, the increasing energy demand and fuel prices are all strong drivers for research into the use of alternative fuels in internal combustion engines. Potential alternative fuels for this application are straight vegetable oils and animal fats. Several manufacturers of medium speed diesel engines show interest. However, due to the difference in fuel properties problems due to the lack of knowledge still exists and engine modifications are required. The study focused on the understanding of the behavior of the fuel during injection in the engine. This was realized through both experimental and numerical work. For the experimental work, a constant volume combustion chamber, equipped with a medium speed diesel injection system, was developed and baptized as the Ghent University Combustion Chamber I (a.k.a. GUCCI). The setup allows the simulation of engine-like conditions and enables several optical diagnostics. Several boundary conditions were carefully analyzed and finally the influence of straight oil on the injection system and atomization were investigated in cold pressurized ambients. The numerical part consisted of the implementation of a spray model as sub-model for an engine simulation tool. The behavior of the model was evaluated for different commonly used diesel and biodiesel surrogates. The conclusions were used to make suggestions for oil surrogates. In a final step, the vaporizing spray model was validated with experiments that were conducted in the constant volume combustion chamber at the Technical University of Eindhoven. The setup conditions were taken as determined by the internationally established engine combustion network (ECN), making the results useful for comparison with similar setups and research at other institutions.